A page layout document is like a canvas that you add text boxes, images, and other objects to, then arrange the objects on the page however you like. Page layout: Used to create documents with a more custom design, like newsletters, books, or posters. You can also add images, charts, and other objects. If you want to add text that’s separate from the main body text, you can add a text box. When you open a word-processing document (or template), you can just start typing. These documents have a body text area where you type, and the text flows from one page to the next, with new pages created automatically when you reach the end of the page. Word-processing: Used to create documents that include mainly text, like reports or letters. Before you choose a template to get started, decide which type of document you want to create:

Pages is a word-processing and page layout app rolled into one.

Intro to word-processing and page layout documents in Pages on Mac